Hi Valda, Ed and Maryam
Not sure if this will help, but Edward Jackson Fitzsimmons married Eleanora O'Donnell daughter of Elliott O'Donnell and Sarah Vize in Limerick. I believe this is the 1864 marriage and the same Elleanora [transcribed Elleanard!] of the 1901 census.
This Edward appears to be the one mentioned in the London Gazette a number of times.
As to their son Edward John Vize Fitzsimmons, I am wondering if the son born 1866 in Galway and the son aged 20 born in Galway in the 1901 census are the same and there has been some recording error. The family seems to have been based around Limerick normally and not Galway, the birth of both in Galway is what makes me suspicious.
Still trying to trace what happened to them but your posts have been very useful!
I am not sure of the connection between Edward and Walter, I would assume brothers as already mentioned, due to the ages, father's name, connection with Limerick.
Sue